Can my epilepsy meds affect a pregnancy test result?

Faye
I have been on a medication called Keppra for nearly 3 years, I am also on other regular medication including, naproxen, diazepam, propranolol half beta, & IBS formulas. 
I had my cool removed a while ago now & I have been as regular as clock work! 
I am not delusional in thinking getting pregnant happens over night but me & my boyfriend had sex every single green day, as we call them & im now 4 days late? With no signs of any spotting? 
I took one clear blue digital & ended up with a book so then took another & it confirmed "not pregnant" 
Had anyone else taking life long medication had false results due to meds?